The present disclosure relates generally to wireless communication systems, and more particularly, to techniques for performing a tune-away on a wireless communication device based on carrier prioritization.
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). LTE is designed to support mobile broadband access through improved spectral efficiency, lowered costs, and improved services using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
LTE carrier aggregation (CA) enables user equipment (UE) to aggregate multiple downlink and uplink carriers using one or more shared radio frequency (RF) resources. A UE may include one or more subscriptions, such as in one or more subscriber identification modules (SIMs), used to connect to different radio access technologies (RATs). One consequence of the UE connecting to a plurality of RATs is that communications for the RATs may sometimes interfere with each other. For example, subscriptions to two RATs on a UE may utilize a shared RF resource (e.g., one or more antennas, one or more receive chain components, etc.) to communicate with each of their respective mobile telephony networks, but only one RAT may use the shared RF resource at a time. The RAT actively using the shared RF resource (“active RAT”) may occasionally be forced to interrupt its RF operations so that the other RAT (“idle RAT”) may use the shared RF resource to perform RF operations. This process of switching access of the shared RF resource is sometimes referred to as “tune-away,” as the RF resource tunes away from a frequency band or channel of the active RAT to tune to a frequency band or channel of the idle RAT.
In a LTE carrier aggregation scenario, the shared RF resources support a primary component carrier (PCC) and one or more secondary component carriers (SCC). The PCC may include both an uplink carrier channel and a downlink carrier channel on a primary cell (PCell), and each of the SCCs may include a downlink carrier channel and additionally, may include an uplink carrier channel on secondary cells (SCells). During a tune-away, the UE or manager of the shared RF resource may select one or more of the SCells to tune away from in order to listen to the idle RAT. Currently, the selection of which SCell to tune-away does not consider the potential impact resulting from tuning away from the selected SCell. Rather, the selection is based on certain default rules. For example, currently, a SCell of an LTE subscription is tuned-away merely because it shares a transceiver with a legacy second-generation (2G) and/or third-generation (3G) subscription. This default tune-away procedure may result in the loss of a critical amount of scheduling information, timing reference, data, and/or broadcast and multicast service (eMBMS) carried by the tuned-away SCell, thereby inadvertently causing loss of LTE connectivity.